Quote:US scientists say they have solved the riddle of why a collection of balancing rocks near the San Andreas fault has never been toppled by earthquakes.

Their decade-long study concludes that quakes can stop or "jump" due to interactions between the San Andreas and the neighbouring San Jacinto fault.

Models show that these interactions sent the biggest vibrations around the rock stacks, leaving them intact.

But the connected nature of the faults has implications for quake planning.